Extruded foam and backer rods have been used for many years and basically provide a compressible filler member which may be placed in a crack to provide a support surface for a sealant. In some cases, open celled backer rods have been used, and in other cases the backer rods are closed celled. The compressibility of the backer rod can also vary with the application.
Some backer rods are manufactured for use with hot sealants, and thus, must retain their integrity when a hot sealant comes in contact therewith. To achieve this result, a cross-linked extruded polyethylene foam product is used. Basically, the extruded foam product undergoes cross-linking after the manufacturing thereof, typically for at least 24 hours. Foam polyethylene cross-linked product that uses carbon particles as a coloring agent has sufficient cross-linking for its intended use within 72 hours of manufacture thereof. The rate of cross-linking can vary, but typically it is desired to have sufficient cross-linking to allow the foam product to work for a hot sealant application, at least within one week of manufacture and preferably within 72 hours of manufacture.
In most cases, cross-linked backer rods for hot sealant applications were manufactured in a black color by adding carbon particles to the polyethylene material, which is eventually extruded to form the backer rod. The carbon particles do not appear to significantly alter the rate of cross-linking.
It is also possible to provide a generally white type product by not adding any color pigments. In some applications, it is desirable to have different color identifications for different applications. It was found that adding non-black color pigments or dyes to the polyethylene material used to form cross-linked product seriously adversely affected the rate of cross-linking, as it appears that the color pigments interfered with this process. The color pigments and dyes used were those typically used in noncross-linked foam polyethylene backer rod products. In particular, it was found that red color pigments of an inorganic type, which would be used in this type of product if it was not cross-linked, seriously delayed the cross-linking process and resulted in either very poor cross-linking or cross-linking that was not substantially completed, even 30 days post-manufacture.
There remains a need to provide a simple arrangement for allowing effective color coding of a cross-linked foamed product, and in particular, such a product that is red in color.